The results of clinical trials to treat neutropenic adults with bacterial or fungal infections are controversial. Some studies have found that granulocyte transfusions are effective in treating bacterial infections but several other have not. While granulocyte transfusions have been effective in treating fungal infections in neutropenic animal models, they have not been effective in treating humans. The ineffectiveness of granulocyte transfusions is likely due in part to the limited quantity of granulocytes that can be collected. Recently, it has been shown that the number of granulocytes collected can be increased two to five-fold by giving donors granulocyte colon-stimulating factor (G-CSF). G-CSF mobilized granulocyte transfusions may be effective in treating bacterial and fungal infections in neutropenic adults. The purpose of this study is to determine if severely neutropenic aplastic anemia patients with bacterial or fungal infections benefit from granulocyte transfusions. Eligible patients will be randomly assigned to either receive conventional antimicrobial therapy or G-CSF mobilized granulocyte transfusions plus conventional antimicrobial therapy. The response of their infection to the treatments as well as their survival will be monitored.